Advances in the environmental analysis of polychlorinated naphthalenes and toxaphene

Recent advances in the analysis of the chlorinated environmental pollutants polychlorinated naphthalenes (PCNs) and toxaphene are highlighted in this review. Method improvements have been realized for PCNs over the past decade in isomer-specific quantification, peak resolution, and the availability of mass-labeled standards. Toxaphene method advancements include the application of new capillary gas chromatographic (GC) stationary phases, mass spectrometry (MS), especially ion trap MS, and the availability of Standard Reference Materials that are value-assigned for total toxaphene and selected congener concentrations. An area of promise for the separation of complex mixtures such as PCNs and toxaphene is the development of multidimensional GC techniques. The need for continued advancements and efficiencies in the analysis of contaminants such as PCNs and toxaphene remains as monitoring requirements for these compound classes are established under international agreements.     

加速溶剂萃取-分子筛固相萃取-气相色谱-串联质谱法测定土壤中多氯萘北大核心CSCD

新污染物引发的环境和健康风险正逐步受到社会各界的广泛关注,我国第十四个五年规划和2035年远景目标纲要明确“重视新污染物治理”。作为新型的持久性有机污染物,多氯萘(PCNs)在土壤中通常处于痕量水平,一般需要经过多层硅胶柱/氧化铝柱等复杂的净化方法,再结合有效的分析手段才能实现准确测定。关注土壤中多氯萘分离分析方法可以为掌握和监管其在土壤中的污染状况提供技术和方法支持。研究以13X分子筛作为固相萃取吸附剂,评价了其对多氯萘的净化效果。研究发现:使用正己烷作为上样溶剂和淋洗剂,10 mL二氯甲烷/正己烷(2∶15,v/v)为洗脱溶剂,可以实现PCNs与脂类大分子等干扰物的选择性分离,且多氯萘内标的平均回收率为56.1%~88.0%。与凝胶渗透色谱法、弗罗里硅土固相萃取柱以及多层硅胶柱/氧化铝柱相比,13X分子筛对土壤提取液的净化效果优于前两种净化方法,可以获得与多层硅胶/氧化铝柱相近的净化效果(53.0%~117.0%),而且操作更加简单,环境更加友好,分析成本大幅度下降。在此基础之上,建立了加速溶剂萃取-分子筛固相萃取,结合气相色谱-三重四极杆质谱法测定土壤中PCNs的分析方法。PCNs同族体的方法检出限为0.009~0.6 ng/g。采用基质加标法评价了本方法的精密度和准确度,CN-3、13、42、46、52、53、73、75在低、中、高加标水平下的平均加标回收率分别为70%~128%、71%~115%和61%~114%,测定结果的相对标准偏差分别为4.2%~23%、6.5%~31%和4.7%~22%,满足痕量分析的要求且平行性较好。从整个分析流程来看,13X分子筛有望成为新污染物净化的新型固相萃取吸附剂,并在土壤新污染物普查中发挥重要作用。     

同位素稀释气相色谱-三重四极杆质谱法测定环境空气中的多氯萘北大核心CSCD

环境空气中的多氯萘(PCNs)一般为痕量水平(pg/m^(3)),要实现其准确定量必然对分析方法的提取、净化和仪器分析提出较高要求。研究通过考察提取溶剂种类、净化流程和色谱-质谱参数,建立了加速溶剂萃取(ASE)-多层硅胶复合中性氧化铝柱的净化方法,并利用同位素稀释气相色谱-三重四极杆质谱(GC-MS/MS)对环境空气中的多氯萘进行测定。同时,通过在采样、提取和进样分析前分别添加同位素内标,开展质量控制和保证。结果表明,在2~100 ng/mL范围内3~8氯萘的平均相对响应因子(RRF)的相对标准偏差(RSD)均小于16%。PCNs同类物的方法检出限为1~3 pg/m^(3)(以样品体积为288 m^(3)计算)。采用基质加标法评价了方法对环境空气样品中PCNs测定的精密度和准确度,低、中、高加标水平下3~8氯萘的平均加标回收率分别为89.0%~119.4%、98.6%~122.5%和93.7%~124.5%,测定结果的平均相对标准偏差分别为1.9%~7.0%、1.6%~6.6%和1.0%~4.8%。整个分析过程中,采样内标和提取内标的平均回收率分别为136.2%~146.0%和42.4%~78.1%,RSD分别为5.6%~7.5%和2.7%~17.5%,满足痕量分析的要求且平行性较好。方法的灵敏度和准确度高,精密度良好,适用于环境空气中3~8氯萘的准确定量测定,可在一定程度上缓解多氯萘监测对高分辨气相色谱-高分辨质谱的依赖,为实现多氯萘的国际履约提供方法支持。     

The effect of diameter on the thermal properties of the modeled shape-stabilized phase change nanofibers (PCNs)

The main objective of the present study is to investigate the effect of diameter on thermal properties of phase change fibers at nanoscale in order to develop a shape-stabilized phase change material (PCM). In this regard, polyethylene glycol/cellulose acetate (PEG/CA) electrospun nanofibers as a model of PCM/polymer structure were electrospun. The electrospinning process was optimized using response surface methodology (RSM) to produce phase change nanofibers (PCNs) with achievable minimum and maximum diameter at nanoscale range. Therefore, PCNs with minimum and maximum diameter (223 nm and 545 nm, respectively) were successfully prepared. According to differential scanning calorimetry (DSC) results, the PCNs sample with maximum diameter exhibited higher efficiency of enthalpy (49.41 %) than the PCNs sample with minimum diameter (46.24 %). On the other hand, a test based on the T-history method revealed that PCNs with maximum diameter enjoy higher thermal insulation effect. Scanning electron microscopy (SEM) as well as DSC results showed that the PCNs samples exposed to thermal cycling test not only preserved their structural durability, but also exhibited about twofold increasing in the efficiency of enthalpy than the non-exposed samples. According to thermogravimetric analysis (TG) results, due to successful entrapping, a fraction of PCMs within the structure of polymer matrix, PCNs sample display greater thermal stability comparing to the pure PCM. The present work emphasises that at nanoscale range, higher diameter of PCNs can present more favorable thermal behavior; suggesting a great potential for advanced applications of thermal energy storage and thermal regulating materials fields.     

Hydrazone-Linked Heptazine Polymeric Carbon Nitrides for Synergistic Visible-Light-Driven Catalysis

Heptazine-based conjugated polymeric carbon nitrides (PCNs) are promising metal-free photocatalysts, yet their synthesis is challenging due to the electron-deficiency and insolubility of heptazine units. Indeed, heptazine-containing polymers have only been prepared through nucleophilic substitution with amines by using toxic cyameluric chloride as the starting material. Herein, we report the novel and environmentally friendly method for preparing heptazine-based mesoporous PCNs with hydrazone links formed through a simple Schiff base condensation of melem-NH₂ and aldehydes. Unlike cyameluric chloride, melem-NH₂ is non-toxic, stable, and can be readily obtained from melem and hydrazine in solution. We demonstrate that the hydrazone linkages and the heptazine units synergistically enhance the photocatalytic activity of PCNs in visible-light-driven aerobic oxidation of benzyl alcohol to benzaldehyde. In particular, the polymer constructed from melem-NH₂ and p-phthalaldehyde shows 17 times more activity than graphitic carbon nitride (g-C₃N₄).     

Microwave-assisted extraction of polybrominated diphenyl ethers and polychlorinated naphthalenes concentrated on semipermeable membrane devices

Microwave-assisted extraction (MAE) has been evaluated as an alternative to dialysis for the extraction of polybrominated diphenyl ethers (PBDEs) and polychlorinated naphthalenes (PCNs) sampled by semipermeable membrane devices (SPMDs), using gas chromatography coupled to tandem mass spectrometry (GC-MS-MS).For MAE optimization a two level full factorial design 2³, plus a centre point, which involves 11 randomized runs was used. The results showed that the temperature had a significant influence on the extraction of the nine PBDEs and four PCNs tested. Also, the solvent volume had a positive influence on the extraction of PBDEs and PCNs, but only in latter compounds, it achieves statistical significance. The time had only statistical significance for the most volatile specie studied, PCN-54. The selected MAE conditions (60 mL of hexane-acetone, 1:1 (v/v), 85 °C, 1 min, two cycles) lead to recoveries between 72 and 91% for PBDEs and between 96 and 103% for PCNs. The applicability of the MAE extraction was tested in field SPMDs deployed for 20 days in a sewage treatment plant.The MAE method developed is about 300 times faster than the conventional dialysis and remarkably reduces the solvent consumption.     

Distributions of Polychlorinated Naphthalenes in Sediments of the Yangtze River,China

The pollution status of polychlorinated naphthalenes (PCNs) in the sediment of the Yangtze River Basin, Asia’s largest river basin, was estimated. The total concentrations of PCNs (mono- to octa-CNs) ranged from 0.103 to 1.631 ng/g. Mono-, di-, and tri-PCNs—consisting of CN-1, CN-5/7, and CN-24/14, respectively, as the main congeners—were the dominant homolog groups. Combustion indicators and principal component analysis showed that the emissions from halowax mixtures were the main contributor to PCNs in sediment, among most of the sampling sites. The mean total toxic equivalent (TEQ) was calculated to be 0.045 ± 0.077 pg TEQ/g, which indicates that the PCNs in sediments were of low toxicity to aquatic organisms. This work will expand the database on the distribution and characteristics of PCNs in the river sediment of China.     

Effect of epoxy resin on rheology of polycarbonate/clay nanocomposites

Polycarbonate/clay nanocomposites (PCNs) were prepared by melt intercalation using epoxy resin as a compatibilizer. The intercalated structure of PCNs was investigated using XRD and TEM. The linear and nonlinear dynamic rheological properties of PCNs were measured by the use of a parallel plate rheometer. The results reveal that the presence of epoxy influences rheological behavior of PCNs significantly. Addition of epoxy can improve dispersion of clay, enhancing the low-frequency viscoelastic responses; while high loadings of epoxy lead to a severe degradation of PC matrix, decreasing the high-frequency responses together with the plasticizing effect of excessive epoxy. Both of these two effects result in invalidity of time-temperature superposition. Moreover, all samples show high sensitivity to both the quiescent and large amplitude oscillatory shear (LAOS) deformation, despite enhanced percolation of tactoids due to the compatibilization of epoxy.     

气相色谱-质谱法测定地下水中多氯萘

建立了地下水中1-氯萘、2-氯萘、1,4-二氯萘、1,2,3,4-四氯萘、1,3,5,7-四氯萘、1,2,3,5,7-五氯萘、1,2,3,5,6,7-六氯萘、1,2,3,4,5,6,7-七氯萘和八氯萘9种多氯萘(PCNs)的气相色谱-质谱(GC-MS)分析方法。对比研究了液液萃取(LLE)和固相萃取(SPE)萃取地下水中PCNs的提取效率,优选二氯甲烷-液液萃取为PCNs检测的前处理方法。在优化条件下,9种PCNs的线性范围为5~100μg/L,各组分的相关系数(r)大于0.995,方法检出限(S/N=3)为4.21~7.41 ng/L,地下水的平均加标回收率为70.7%~112%,相对标准偏差(RSD,n=5)均小于9.9%。该方法已用于地下水样中多氯萘的检测。     

多氯萘的气相色谱保留指数与其结构参数的定量关系

在B3LYP/6-31G*水平上计算了76个多氯萘分子,将计算得到的结构参数和热力学参数作为理论描述符引入到与气相色谱保留指数(RI)相关的多元回归分析中,建立了拟合度高、物理意义明确、预测能力强的保留时间-结构参数的相关方程(模型Ⅰ)(r2=0.9957);再以氯原子的取代个数和相互位置作为理论描述符,得出另一模型(模型Ⅱ)(r2=0.9967)。找出了影响多氯萘保留时间的主要因素。     

A Study in Red: The Overlooked Role of Azo-Moieties in Polymeric Carbon Nitride Photocatalysts with Strongly Extended Optical Absorption

The unique optical and photoredox properties of heptazine-based polymeric carbon nitride (PCN) materials make them promising semiconductors for driving various productive photocatalytic conversions. However, their typical absorption onset at ca. 430–450 nm is still far from optimum for efficient sunlight harvesting. Despite many reports of successful attempts to extend the light absorption range of PCNs, the determination of the structural features responsible for the red shift of the light absorption edge beyond 450 nm has often been obstructed by the highly disordered structure of PCNs and/or low content of the moieties responsible for changes in optical and electronic properties. In this work, we implement a high-temperature (900 °C) treatment procedure for turning the conventional melamine-derived yellow PCN into a red carbon nitride. This approach preserves the typical PCN structure but incorporates a new functionality that promotes visible light absorption. A detailed characterization of the prepared material reveals that partial heptazine fragmentation accompanied by de-ammonification leads to the formation of azo-groups in the red PCN, a chromophore moiety whose role in shifting the optical absorption edge of PCNs has been overlooked so far. These azo moieties can be activated under visible-light (470 nm) for H₂ evolution even without any additional co-catalyst, but are also responsible for enhanced charge-trapping and radiative recombination, as shown by spectroscopic studies.     

加速溶剂萃取-硅胶柱净化-碱性氧化铝柱分离-气相色谱三重四极杆质谱法测定土壤中的二噁英类化合物

建立了加速溶剂萃取(ASE),酸性硅胶柱、复合硅胶柱及碱性氧化铝柱纯化分离,气相色谱-三重四极杆质谱测定土壤中二噁英/呋喃(PCDD/Fs)、多氯联苯(PCBs)、多氯萘(PCNs)的分析方法.选用正己烷-二氯甲烷(50∶50, V/V)作为ASE的提取溶剂,设定提取温度为120℃,加标回收实验表明本方法可行.用100 mL正己烷-二氯甲烷(95∶5, V/V)及50 mL正己烷-二氯甲烷(50∶50, V/V)依次淋洗碱性氧化铝柱,得到组分A(PCBs及PCNs)与组分B(PCDD/Fs),实现了PCDD/Fs与另外两种化合物的分离,排除了同系物间及其它杂质的干扰.使用同位素稀释-气相色谱三重四极杆质谱法(GC-MS/MS), 在选择反应监测(Selected reaction monitoring, SRM)模式下测定PCDD/Fs、PCBs和PCNs,3种化合物的仪器检出限(LOD)范围分别为0.04~0.25 μg/L, 0.10~0.20 μg/L和0.01~0.05 μg/L,目标物平均相对响应因子(RRF)的相对标准偏差(RSD)均小于13%.基质土加标实验中,3种化合物13C标记的同位素内标回收率的范围分别为50%~95%,51%~103%, 49%~74%.实际样品的分析结果表明,PCDD/Fs、PCBs及PCNs在土壤样品中的总含量范围分别为16.1~1148 pg/g、6.6~152.6 pg/g及10.9~99.5 pg/g,且样品测定结果与高分辨质谱测定结果相吻合.     

Analysis of organochlorines in harbor seal (Phoca vitulina) tissue samples from Alaska using gas chromatography/ion trap mass spectrometry by an isotopic dilution technique

A gas chromatography/ion trap mass spectrometry (GC/ITMS) method was developed for the determination of organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs) and polychlorinated naphthalenes (PCNs) in harbor seal (Phoca vitulina) tissues. Tissue samples were homogenized, lyophilized and fortified with (13)C-PCBs 28, 123, 169 and 170, and then extracted with an accelerated solvent extractor with a mixture of hexane and methylene chloride (1:1, v/v). After lipid removal using a 40% H(2)SO(4)-modified silica gel column, all organochlorines were collected in one fraction and further fractionated with an activated carbon/silica gel (1:20) column into a first fraction containing OCPs, non-coplanar PCBs and (13)C-PCBs 28, 123 and 170, and a second containing PCNs, coplanar PCBs and (13)C-PCB 169. Prior to GC/MS/MS analysis, (13)C-PCB 169 was added into the first fraction as an injection standard and (13)C-PCB 170 into the second fraction to calibrate the recoveries of the fortified internal standards. This method can effectively eliminate matrix interferences, and has high selectivity and sensitivity. Recoveries averaged 45-86% for OCPs with relative standard deviations (RSDs) of 2-14%, 52-137% for PCBs with RSDs of 3-29% and 36-152% for PCNs with RSDs of 7-29% from lard and chicken heart samples, which were used as alternative matrices to harbor seal samples in recovery studies. The limits of detection for OCPs, PCBs and PCNs were 0.7-1.9, 1.5-8.9 and 0.5-10 pg/g dry weight, respectively. This method can be used to analyze OCPs, PCBs and PCNs in harbor seal blubber, liver and kidney samples.     

Glutathione-triggered non-template synthesized porous carbon nanospheres serve as low toxicity targeted delivery system for cancer multi-therapy

Nanomaterial based drug delivery system have received great attention in clinical application due to their high therapeutic efficacy and lower side effects than classical method, multi-functional nanomaterial also have shown the excellent performance at cancer theranostic and durg tracking in vivo and in vitro. However, most of these works are influenced by the bio-toxicity of applied nanomaterials, which could influence the diagnostic results and treatment effect. Therefore, we have prepared a high biocompatibility porous carbon nanospheres (PCNs) based nano-system (PCN-siRNA-DOX-FA) for targeted drug delivery and theranostic. The surface modifications have increased dispersion and stability of the PCNs, and folic acid (FA) had enhanced the active target ability for FA receptor positive cell lines. Moreover, through the siRNA structure and doxorubicin (DOX) loading, biological and chemical combined multi-therapy was achieved in cancerous cells. This constructed nano-system could positively improve the biotoxicity problem of nanomaterial and provide a potential platform for clinical cancer theranostic applications.     

On the interlayer spacing collapse of Cloisite 30B organoclay

When used as a nanofiller for the preparation of polymer/clay nanocomposites (PCNs), Cloisite^® 30B (30B) often undergoes a d-spacing collapse, as demonstrated by a shift to wider angles of the XRD basal reflection. Such collapse has been variously attributed to organoclay contamination or, more often, to thermal degradation of the organic modifier with expulsion of the volatile products from the galleries. In this work, several PCNs loaded with 30B have been prepared by melt compounding, using different polymer matrices, and have subsequently been subjected to dissolution in appropriate solvents followed by precipitation in excess non-solvent and room temperature drying. An XRD analysis of the products has shown that this treatment makes the 30B basal plane reflection go back to the original angular position. These experiments indicate that, contrary to the situation prevailing when 30B is subjected to thermal treatments at temperatures well above the onset of degradation (∼180 °C), the d-spacing collapse observed after melt compounding 30B with polymer matrices at moderate temperatures is in fact a reversible phenomenon probably due to rearrangement of the alkyl chains of the clay modifier in a disposition intermediate between bilayer and monolayer.     

微波萃取/GC-MS法对电子电气产品中多氯萘的测定

建立了微波萃取/GC-MS法检测电子电气产品中多氯萘的方法。将破碎后的样品以甲苯为溶剂进行微波萃取,萃取液经硅胶小柱净化、平行蒸发定量浓缩后采用气相色谱-质谱法测定多氯萘的含量,外标法定量。优化了样品前处理条件,包括前处理方式、微波萃取溶剂、萃取时间,以及净化小柱的选择。对于8种含不同氯原子数的多氯萘,在1~50 mg/L范围内,线性关系良好,相关系数均大于0.995;方法定量下限为0.2~1.0 mg/kg,相对标准偏差为2.7%~7.2%,回收率为77%~112%。该法操作简便、分析迅速、结果准确,可以满足对电子电气产品中多氯萘的定性确证和定量分析。     

Polychlorinated naphthalene concentrations and profiles in cheese and butter,and comparisons with polychlorinated dibenzo-p-dioxin,polychlorinated dibenzofuran and polychlorinated biphenyl concentrations

Polychlorinated naphthalenes (PCNs) are candidates for inclusion in the Stockholm Convention on persistent organic pollutants. PCNs are structurally and toxicologically similar to 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD) and its analogues. Intake in food is considered to be an important human exposure pathway for PCNs. In this preliminary study, cheese and butter samples were analysed for PCNs, polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and polychlorinated biphenyls (PCBs) using an isotope dilution gas chromatography high-resolution mass spectrometry method. The aim of this study was to evaluate the PCN concentrations in the cheese and butter samples and to compare them with the PCDD, PCDF and PCB concentrations. The PCN concentrations were 5.6–103 pg g^?1 of wet weight in the seven cheese samples tested and 5.0–199 pg g^?1 of wet weight in the seven butter samples tested. The mass concentrations of lower chlorinated congeners were greater than those of the higher chlorinated congeners. Congeners of CN45/36, CN27/30 and CN33/34/37 were much more abundant than other congeners found in tetrachlorinated PCNs. Congeners of CN51, CN66/67 and CN73 were determined to be the predominant congeners in penta-, hexa- and heptachlorinated homologs, respectively. The PCNs contributed around 5% of the total PCN, PCDD, PCDF and PCB toxic equivalence (TEQ) values. CN73 was found to be the dominant PCN congener and contributed more than 40% to the PCN TEQ value. Congeners CN66/67, CN69 and CN63 were also found at relatively high levels. The PCB congener CB118 was the predominant congener (by mass-based concentration) of the 12 dioxin-like PCBs (dl-PCBs). The PCBs contributed 53.8% of the total TEQ, and congener CB126 contributed more than any other compound that was analysed to the total TEQ. The PCDDs and PCDFs contributed 11.6% and 29.7% of the total TEQ values, respectively.